Electrical switch



Nov. 30, 1954 R. D. HANCOCK 2,695,938

ELECTRICAL SWITCH Filed June 25, 1951 United States Patent O ELECTRICAL SWITCH Robert D. Hancock, Compton, Calif., assigner-:to-Northrop Aircraft, Inc., Hawthorne, Calif., a corporation of California Application June 25, 1951, Serial No. 233,377

7 Claims. (Cl. 200-152) The present invention relates to electric switches, and more particularly to a method and means for making and breaking electrical contacts.

One of the objects of the present invention is to provide a reliable electrical switch capable of rapid, ellicient operation.

Other objects and advantages will become apparent as the disclosure continues.

Briefly as to method, the present invention comprises the steps of confining two masses of mercury, connecting the mercury masses together through a mercury column of capillary size, and then varying the amount of pressure exerted upon the mercury in one of the masses between pressure where the mercury is continuous through the capillary column and a pressure where the mercury is separated in the capillary column. It has been found that, under these conditions, the mercury will always separate only in the capillary column, thus providing a desirable mercury to mercury contact.

In one preferred apparatus form, the switch of the present invention employs an enclosure shaped to form a pair of chambers joined together through a capillary tube. The chambers are filled with a conductive fluid such as mercury, which is continuous from one chamber through the capillary tube into the adjoining chamber. A contact extending through the enclosure is positioned in each chamber on either side of the capillary, and means are provided to vary the amount of pressure exerted upon the mercury in one of the chambers between a pressure where the mercury is continuous through the capillary, and a pressure where the mercury is separated in the capillary, whereby a conductive path for electricity between the contacts can be made or broken by actuating the pressure varying means.

Figure 1 is a longitudinal sectional view of one embodiment of the present invention in the closed state.

Figure 2 is a longitudinal sectional view of the embodiment of the present invention shown in Figure l in the open state.

Referring to Figure l, one preferred embodiment of the present invention is shown wherein a non-resilient enclosure of a vitreous material such as glass for example, is shaped to form two chambers 11 and 12 which are joined together to communicate, one with the other, through a capillary passage 13 which has a coating 14 of silicone compound, so that mercury to be added will not tend to wet the glass. It should be here noted that the diameter of the capillary passage as shown in Figures l and 2 is greatly exaggerated for ease of illustration.

The enclosure 10 is filled with a conductive fluid 15, preferably mercury; the mercury 15 in one chamber 11 being continuous through the capillary passage 1.3 with the mercury 15 in the adjoining chamber 12. The sealed tubulation 16 in the exterior wall of the enclosure 10 is for the purpose of filling the enclosure with clean mercury 15 by methods which are well known in the art.

A contact 17 is sealed in the wall of the enclosure 10 on each side of the capillary passage 13, having one end thereof extending into the mercury 15 in each chamber 11 and 12, the other end thereof extending to the exterior of the enclosure 10.

A bellows 19, of a material which is compatible with mercury, is integrally connected and sealed to form a portion of one of the chambers 11 of the enclosure 10. The bellows 19 is capable of flexing to increase the volume of the chamber 11, thereby changing the pressure ICC which is exerted upon the mercury 15 so that the mercury 15 will be separated in the capillary passage 13, as shown in Figure 2, to break the conductive path for electricity through the mercury 15. When the bellows is returned to'normal state, i. e., unexed, the chamber 11 returns to normal capacity, increasing the pressure upon the mercury 15 so that the mercury reunites in the capillary 13, thereby reestablishing the conductive path for electricity through the mercury 15. The mercury always breaks in the capillary tube, and provides a mercury to mercury contact.

A lever 20, pivotally connected at one end thereof to the end of the bellows 19, is rockable about a central pivot 21 to ex the bellows 19 for operation of the switch. A spring 22 connected at one end thereof to solid support 24, the other end thereof being connected to the end of the lever 20 opposite the end which is connected to the bellows 19, can be provided to maintain the switch in closed position. By placing the spring 22 on the opposite side of the lever 20 as shown by dotted line 22a, the switch can then be maintained in the open position. Means necessary to move the lever 20 to flex the bellows 19 are available in a number of devices such as solenoids, magnetostrictive rods, etc., and one pre` ferred use for the device is for high speed direct current interruption.

It can be seen that a novel electric switch having a number of distinct advantages is thus provided by the present invention.

While in order to comply with the statute, the invention has been described in language more or less specific as to structural features, it is to be understood that the invention is not limited to the specific features shown, but that the means and construction herein disclosed comprise the preferred form of putting the invention into effect, and the invention is therefore claimed in any of its forms or modifications within the legitimate and valid scope of the appended claims.

What is claimed is:

1. An electrical device of the kind containing two bodies of mercury, contact means positioned in each body of mercury, and a length of capillary tubing adapted to be occupied by mercury forming part of said bodies, comprising: chambers arranged coaxially with and separated by the capillary tubing, one of said chambers being variable in volume; contacts in said chambers; means for completely filling said chambers and capillary tubing with mercury while the volume of said variable volume chamber is reduced so as to prevent the presence of any other medium than mercury in the envelope; and means for varying the volume of the variable volume chamber to provide at times a continuous mercury path between said contacts and at other times to interpose a gap in said path.

2. An electrical device as set forth in claim l and in which one of said chambers is formed with a side tube through which the switch envelope may be completely filled with mercury after the switch parts have been assembled, the tube being then sealed off leaving the switch completely lled with mercury.

3. An electrical device as set forth in claim l and in which a bellows is fitted to at least one of said chambers, the switch envelope and said bellows being completely filled with mercury.

4. An electrical device as set forth in claim l and addition comprising a coating of silicone compound on the inside of the capillary tube to prevent wetting of the walls of the tube by the mercury.

5. An electrical device as set forth in claim 3 and in which resilient means are provided normally exerting tension upon said bellows to provide a normally open switch; and means for relieving the tension of said resilient means to at times permit the mercury in said capillary tube to unite to provide a closed path.

6. An electrical device as set forth in claim 3 and in which resilient means are provided normally exerting pressure upon said bellows to effect junction of the mercury in the capillary tube and to provide a normally closed switch; and means for relieving the pressure exerted by said resilient means to thereby increase the volhaving an envelope urne of said envelope to effect interruption of the current Number Name Date path through the switch. 1,504,997 Walker Aug. 12, 1924k 7. An electrical device as set forth in claim 5 and in 1,614,621 McCabe Jan. 18, 1927 which said resilient means are limited in stroke to keep, 2,150,053 Chilowsky Mar. 7, 1939 at all times, mercury within the capillary tube. 5 2,163,709 Schimkus June 27, 1939 2,332,947 Strornmer Oct. 26, 1943 References Cited in the file of this patent FOREIGN PATENTS STATES PATENTS Number Country Date Number Name D l0 22,717 Great Britain Oct. 1898 ate 1,037,732 Crist et fal. Sept. 1912 of 1897 

